Specifications

Circuit Description
DS360 Ultra Low Distortion Function Generator
6-4
Microprocessor and System Clocks
U401 is a Z80 general purpose microprocessor. It is clocked at 10.6 MHz, generated
from the main system clock. The 16 bit address space (A0-A15), is divided into ROM
(U402) and RAM (U403) by U413. The memory map for ROM and RAM is as follows:
ROM $0000 to $CFFF
RAM $D000 to $FFFF
U407 (74HC154) generates all chip selects for the system. U404 and U406 are system
status and control ports, respectively. U416 is the digital output control port (for U201).
U415-A or’s together all of interrupt signals to generate the maskable interrupt to the
Z80.
U405 (8254) is a triple 16 bit counter, used to generate the real time clock (1.67 ms), set
the RS232 baud rate (for U604) and speaker tones (for SP401). The baud rate can range
from 300 to 19.2k baud. D401, D402, and BT101 provide the battery backup to the
system RAM (U403). Q402, Q403 and associated resistors and capacitors generate the
power on reset and power fail shut down.
U408 is a 32.333 MHz 25 ppm oscillator. It is buffered by U411 to three different paths,
the system clocks, DSP control logic and D/A sync control. This is to avoid any signal
contamination due to reflections or load variations. The main clock is divided down by
U409 and U410 to provide the different system clocks.